Tunable Nonadiabatic Excitation in a Single-Electron Quantum Dot

National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 0LW, United Kingdom.
Physical Review Letters (Impact Factor: 7.51). 03/2011; 106(12):126801. DOI: 10.1103/PhysRevLett.106.126801
Source: PubMed


We report the observation of nonadiabatic excitations of single electrons in a quantum dot. Using a tunable-barrier single-electron pump, we have developed a way of reading out the excitation spectrum and level population of the dot by using the pump current as a probe. When the potential well is deformed at subnanosecond time scales, electrons are excited to higher levels. In the presence of a perpendicular magnetic field, the excited states follow a Fock-Darwin spectrum. Our experiments provide a simple model system to study nonadiabatic processes of quantum particles.

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    • "However, since the devices investigated in this study were similar to those in [22], we used the highest field accessible with our experimental system, 14 T. Previous high-resolution measurements using sine wave drive could not be extended above f ≈ 350 MHz because the quantised plateau degraded with further increase in f [16]. The general mechanism for this is not currently understood, although clear signatures of backtunneling due to non-adiabatic excitation at high f have been seen in some samples [24]. To extend the pump operation range to higher frequencies, we developed a technique using an arbitrary waveform generator (Tektronix AWG7122B) to generate a custom V G1 (t) waveform . "
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